BAGHDAD, Iraq (CNN) -- U.S. Defense Secretary Robert Gates has dismissed as "ridiculous" any suggestion that the resignation of America's military chief in the Middle East signals the United States is planning to go to war with Iran.

Adm. William Fallon had been serving as chief of U.S. forces in the Middle East and Central Asia since 2007.

Adm. William Fallon resigned Tuesday as chief of U.S. forces in the Middle East and Central Asia after just a year in the post, citing what he called an inaccurate perception that he is at odds with the Bush administration over Iran.

Fallon, the head of U.S. Central Command, was the subject of a recent Esquire magazine profile that portrayed him as resisting pressure for military action against Iran, which the Bush administration accuses of trying to develop nuclear weapons.

"Although I don't believe there have ever been any differences about the objectives of our policy in the Central Command area of responsibility, the simple perception that there is makes it difficult for me to effectively serve America's interests there," Fallon said.

"Admiral Fallon reached this difficult decision entirely on his own. I believe it was the right thing to do, even though I do not believe there are in fact significant differences between his views and administration policy," Gates said.

Gates said repeatedly that he believed talk of Fallon opposing President George W. Bush on military action against Iran was mistaken.

Fallon, a 41-year veteran of the Navy, took over as chief of Central Command in early 2007. Gates said he will be replaced by Lt. Gen. Martin Dempsey, his deputy, who commanded an Army division in Iraq in the early days of the war and led efforts to train the Iraqi military.

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The perception that Fallon has opposed a drive toward military action against Iran from within the Bush administration dates to his confirmation hearings in January 2007, when he told the Senate the United States needed to exhaust all diplomatic options in its disputes with the Islamic republic.

But he also has said the United States would be able to take steps if Tehran were to attempt to block the Strait of Hormuz, the outlet of the Persian Gulf and a choke point for much of the world's oil.

And he recently told CNN that the United States was looking for a peaceful settlement to disputes "in every case."

"We're trying to encourage dialogue and find resolution," he said. "In fact, that's our message to the Iranians out here, given that everybody is nervous and anxious about their activities, is to come forth and explain what they are doing with all the people in the region."

On Tuesday, Gates said: "We have tried between us to put this misperception behind us over a period of months and, frankly, just have not been successful in doing so."

In a written statement, Bush praised Fallon for helping "ensure that America's military forces are ready to meet the threats of an often troubled region of the world.

"He deserves considerable credit for progress that has been made there, especially in Iraq and Afghanistan."

But Democratic Senate Majority Leader Harry Reid said Fallon's resignation showed that independent views "are not welcomed in this administration."

"It is also a sign that the administration is blind to the growing costs and consequences of the Iraq war, which has so damaged America's security interests in the Middle East and beyond," said Reid, D-Nevada. "Democrats will continue to examine these matters very closely in the coming weeks and months."E-mail to a friend